Pocket-protractor.



J. SHARPE.

POCKET PEOTRAOTOR. APPLICATION FILED JULY 19, 1912 Patented May 27,1913.

wi bvmomk I JOSEPH SHABPE, OF THE UNITED STATES ARMY.

POCKET-PROTRACTOR.

Specification of Letters Patent.

Patented May 27, 1913.

Application filed July 19, 1912. Serial No. 710,528.

To all whom it may concern:

Be it known that I, JOSEPH SHARPE, of the United States Army, haveinvented certain new and useful Improvements in Pocket- Protractors; andI do hereby declare the following to be a full, clear, and exactdescription of the invention, such as will enable others skilled in theart to which it appertains to make and use the same.

This invention relates to pocket protractors.

The object of the invention resides in the provision of a prot-ractor ofthe character named which will occupy a minimum space and which may beutilized with facility for solving a wide range of mechanical problemswithout resorting to the use of mathematics.

With the above and other objects in view, the invention consists in thedetails of construction and in the arrangement and combination of partsto be hereinafter more fully described and particularly pointed out inthe appended claim.

In describing the invention in detail, reference will be had to theaccompanying drawings wherein like characters of reference denotecoresponding parts in the several views, and in which,

Figure 1 is a plan view of the protractor constructed in accordance withthe invention, Fig. 2, a section on the line 22 of Fig. 1, Fig. 3, aplan view of the rotatable ring of the protractor detached, and Fig. 4:,aplan view of the detachable bar for effecting the rotation of theprotractor ring.

Referring to the drawings the protractor is shown as comprising outerring members A and B and an intermediate ring member 0. The outer ringmember A has its inner face provided at each side with annular recesses10 and 11, while the ring C is provided with a flange 12 on the outeredge thereof which seats in the recess 10. The ring C is held againstdisengagement from the ring A by means of the outer ring B, which latteris secured against the inner face of the ring A in overlapping relationto the flange 12 and recess 11. In this manner the ring C is rotatablewithin the rings A and B. The outer face of the ring B is provided withdegree graduations 13. Connecting the inner edge of the ring C is adiametrical cross bar 14 the side edge 15 of which is beveled andcoincides with a given diameter of the ring C. This diametrical crossbar 14 is provided with graduations 16 which read from the center ofsaid cross bar outwardly in each direction. The ring C is provided on itouter face with lines 17 and 18 which register with the side edge of thecross bar 14L which coincides with a given diameter of a ring C. Theouter face of the ring C is also provided with lines 19 and 20 whichcoincide with a diameter of the ring C disposed at right angle to thebar 14. The ring C is adapted to be rotated within the rings A and B bymeans of a graduated arm 21 one end of which is reduced as at 22 forminga resultant shoulder and this shoulder is provided with a recess 24forming a resultant tongue 25. In applying the arm 21 to the instrumentthe reduced portion thereof is disposed in overlapping relation to thecross bar 1 1 and the tongue 25 inserted in the recess 11 when the armis secured to the cross bar 14 by means of screws 26. By thisconstruction it will be apparent that the ring C can be readily rotatedby means of the arm 21. Mounted in the arm 21 is an adjusting screw 27which is adapted to engage the outer face of the ring A so as to lockthe ring C against rotation.

What is claimed is:

A pocket protractor comprising a pair of outer rings one of which hasits inner face provided with annular recesses at each edge, and itsouter face graduated, an intermediate ring having its outer edgeprovided with a flange seated in the innermost recess of said outer ringwhereby said intermediate ring is rotatably mounted between the outerrings, a graduated diametrical cross bar connecting the inner edge ofthe intermediate ring and having one side edge coincident with adiameter of said ring, a graduated arm having one end reduced andoverlying said cross bar, means connecting said reduced end of said armto the cross bar, and a tongue on said arm slidable in the outermostrecess of the outer ring.

In testimony whereof, I affiX my signature, in presence of twowitnesses.

JOSEPH SHARPE.

Witnesses:

JOHN H. CI-IAPPLE, EUGENE A. LA FLAME.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents, Washington, D. G.

